1. Field of the Invention
The present invention relates to a binding apparatus, and more particularly relates to a binding apparatus capable of binding sheets of cut paper printed and outputted by a printing machine so that the sheets of cut paper can be bound and sorted by a number predetermined for each job.
2. Description of the Related Art
With the recent progress in information processors, it is necessary to sort a large number of sheets of paper printed and outputted by a printing machine. For example, in the case of a high speed printing machine for printing sheets of cut paper in a computer center, it is necessary to sort the sheets of outputted cut paper for each job as an after-treatment. Therefore, it is desired to reduce labor and automate the after-treatment after the sheets of cut paper have been outputted from the printing machine.
In the case of a conventional printing machine for printing sheets of cut paper, sheets of printed cut paper are sorted for each job, that is, the after-treatment is conducted for each job-offset. With reference to FIG. 1, this after-treatment for each job-offset will be explained as follows.
An example of the structure of a conventional printing system PS is shown in FIG. 1. The conventional printing system PS includes a sheet hopper H to feed sheets of cut paper S one by one, a printing machine P to print on the sheets of cut paper S, and a sheet after-treatment unit A to conduct an after-treatment on the sheets of printed cut paper S.
The printing machine P includes a photoreceptor drum 1, development unit 2, fixing unit 3, cleaner 4, charging unit 5, optical unit 6, transfer separator 7, and conveyance unit 8. The optical unit 6 includes a mirror motor 61, polygonal mirror 62, beam emitting mirror 63, reflection mirror 64, and laser diode 65.
The photoreceptor drum 1 is electrically charged by the charging unit 5, and a latent image is formed on the photoreceptor drum 1 by a laser beam sent from the optical unit 6. This latent image is developed by the development unit 2, so that a toner image is formed. Then, the sheets of cut paper S are successively fed one by one to the printing machine P from the sheet hopper H by the roller R. The sheet of cut paper S sent from the sheet hopper H is conveyed by the conveyance roller Ri provided on the printing machine P side, and arrives on the photoreceptor drum 1. At this time, the toner image on the photoreceptor drum 1 is transferred onto this sheet of cut paper S by the transfer separator 7. In this connection, in order to stabilize the formation of the latent image, a portion of the laser beam is taken out by the beam emitting mirror 63 so as to check the intensity of the laser beam.
This sheet of cut paper S is further conveyed by the conveyance unit 8, and the toner image on the sheet is fixed by a heat roller having a heater in the fixing unit 3. After that, the sheet of cut paper S is conveyed by the conveyance roller R.sub.0 onto a stack table 9 in the sheet after-treatment unit A so as to be stacked. At this time, in the conventional printing system PS, the stack table 9 is laterally shifted for each job (job-offset).
Due to the foregoing operation, the sheets of printed cut paper S are stacked on the stack table 9 in such a manner that several tens or several hundreds of sheets are formed into a bundle and stacked in an uneven manner as shown in FIG. 1.
However, the following problems may be encountered in the conventional printing system PS constructed in the aforementioned manner. That is, in the case of the conventional printing system PS, the printed sheets are sorted by job-offset, however, the following problems are caused.
As shown in FIG. 1, the printed sheets S are only stacked on the stack table 9 forming an off-set for each job. Accordingly, when these sheets of cut paper S are handled, there is a possibility that the bundles of sheets S collapse and disperse. When an operator takes the printed and outputted sheets S, the operation of the printing system PS must be stopped for safety. Therefore, the printing speed is substantially decreased.
In order to solve the aforementioned problems caused in the process of job-offset, the printed sheets are stapled by a stapler as an after-treatment. However, the following problems are encountered in the after-processing conducted by the stapler.
(1) Since the length of staples is limited, the number of sheets to be stapled is limited to a small number.
(2) When stapled sheets S are stacked, the thickness of the stapled portion is increased, so that the bundle of sheets S is inclined, which is disadvantageous in handling.
As described above, the conventional after-treatment mechanisms such as a stacking mechanism to use job-offset and a stapling mechanism to use a stapler are not suitable for a cut sheet printing system to print a large number of sheets at high speed to be used in computer centers.